Thursday 25 March 2010 15.28 EDT
First published on Thursday 25 March 2010 15.28 EDT

For a man with family treasures worth a fortune, Jaume Grau-Pla was somewhat cavalier about security. His 12th-century relics and jewels are worth hundreds of millions of pounds, a dazzling collection that others might have locked away or consigned to a bank vault complete with an expensive insurance policy.

Grau-Pla had an altogether more homespun solution: he stuck all the pieces in a derelict mansion in the Catalan interior and guessed that thieves would never suspect anything of any value was there.

He guessed wrong.

Today it emerged that treasures worth €300m (£270m) had been stolen from the country house. Fortunately for the wealthy aristocrat, most of the booty was recovered. Two of the three suspected thieves were arrested.

"I keep the house run-down on purpose as a way to camouflage the high-value collection I keep inside," Grau-Pla told El País newspaper. "Only those who had been inside the house knew what was kept there. Many of the things are invaluable. No amount of money could buy them."

Grau-Pla only realised that the collection had gone when he visited one weekend and found the glass cases empty.

Police who detained the thieves were themselves stunned by the tiaras, necklaces, rings and other jewellery that they discovered. They said they were happy to believe the aristocrat's own €300m valuation of the collection.

A nosy part-time gardener who peered through the windows at the glinting collection had apparently come up with the idea of breaking in to see what was inside. He was allegedly helped by the two young suspects detained by police.

"These were inexperienced, common crooks who thought they were breaking into any old uninhabited house in the countryside," a police spokesman said.

Police said the suspected thieves, who had little idea of the value of their haul, were captured after they began to squabble over the loot. The gardener broke into the house belonging to his two partners in crime and they, in turn, called the police.

Police then discovered an antique gold coin from the aristocrat's collection hidden inside a sock. The rest of the booty was found in an old sack that had been hidden in a gully in open countryside nearby.

The sack contained a dozen silver diadems decorated with diamonds, pearls and rubies. There were also silver jars, trays and cutlery, as well as a 12th-century religious relic supposedly containing a rib belonging to St Waldesca.

Police said they were still looking for the gardener, who they said had disappeared with €4.5m worth of jewels and antiques.

"This has been totally surreal, because hardly anyone here knew about the treasure," said the local mayor, Pere Solanellas.